1. Field of the Invention
The present invention relates to a method of ensuring the quality of service of the network bandwidth, and more particularly, to a network system capable of dynamically controlling the data flow such that different bandwidths can be assigned according to different service classes when the number of physical queues is reduced.
2. Description of the Related Art
IETF (internet engineering task force) specifies two mechanisms, an integrated service (Intserv) and a differentiated service (Diffserv), to provide an appropriate service according to networks having different properties such that different streams (e.g. video streams or audio streams) can be transferred smoothly.
In the Diffserv, six bits of TOS (Type of Service) in the IP header are utilized to indicate different service classes. The above-mentioned six bits are differentiated service code point (DSCP). If the service provider intends to provide different traffics corresponding to different qualities of service (QoS), the service provider sets a specific DSCP in the header as each DSCP represents a specific service class and a corresponding operation. Moreover, in a DiffServ model, different DSCPs correspond to different packet forwarding methods called PHB (Per-hop Behavior) in a router, and the packet is divided into three PHBs according to its traffic property. The three PHBs are as follows:
1. Expedited Forwarding (EF) PHB;
2. Assured Forwarding (AF) PHB; and
3. Best Effort (BE) PHB.
The above-mentioned PHBs represent three different service classes respectively, where each class can be indicated by the aforementioned DSCP. Therefore, when a packet enters a Diffserv domain, an ingress router classifies and labels the packet by setting the DSCP in the DS field of the packet. Then, a core router in the Diffserv domain provides different forwarding methods and QoSs according to different service classes. As Diffserv only performs a classifying service on the packet, the core router does not additionally record forwarding information corresponding to each route of traffic. Thus, the packets cannot be efficiently managed in a conventional Diffserv domain.
In addition, take a conventional network system supporting Diffserv as an example, assuming that the network system supports at least six different service classes, where a highest class of the six service classes is an EF class and the second highest class is an AF class. The AF class is further divided into four different classes according to different traffic properties. The rest class (the lowest class) is a BE class. A forwarding unit 10 of the above-mentioned network system is shown in FIG. 1. The forwarding unit 10 at least includes a packet input end 11, a classifier 12, a plurality of (as many as the number of service classes) meters/droppers 13, a plurality of (as many as the number of service classes) output queue devices 14, and a packet output end 15.
The packet input end 11 receives packets from the network. The classifier 12 classifies the packets according to the traffic properties of the packets. The meter/dropper 13 measures the data flow of the packets and drops some packets when the queue is full or when some specified conditions are satisfied. At last, the output queue devices 14 perform queue management on the packets corresponding to different classes, and then the packet output end 15 outputs the packets.
According to the above disclosure, in a conventional network system supporting Diffserv, the physical output queue devices 14 have to be established as many as the number of the supported service classes. Therefore, it is not efficiency utilizing the aforementioned network.